In recent years, interest in environmental issues has been rising. To meet with this, the need has been increasing for processing a workpiece while making the amount of chemical as small as possible. For example, in the processing field, achievement of a practical dry cutting technology has become urgent business. To efficiently cool the heat generated due to the processing, a cooling system utilizing the heat of vaporization of a small amount of water and large amount of air is necessary.
In the past, when converting a liquid to a mist (fine drops of liquid) and coating the processed surface or cooling the processed object, for example as shown in FIG. 4A, an atomization apparatus comprised of a pump A, chemical tank B, and nozzle C is used. By pressurizing a chemical in the chemical tank B, feeding it by the pump A to the small diameter nozzle C, and spraying the chemical from the nozzle C, it is converted to a mist. As a means for introducing a gas to this system to create a mixture of the atomized liquid and gas, a nozzle C for mixing a liquid and gas called a “two-fluid nozzle” is used and a high pressure gas (mainly high pressure air) is introduced into the two-fluid nozzle so as to create an atomized gas (cooling gas) converted into a micro-mist by the rapid expansion and diffusion action of the high pressure gas.
The distribution of the generated mist of the micro-mist created by this means (distribution of particle size and number of generated particles), as shown by the graph of FIG. 4B, includes a broad range of particles from large particles of about 70 μm to small particles of not more than 5 μm, has an average particle size of 30 μm or so, and differs in generated mist distribution due to the distance from the nozzle as well. Further, if using this atomization apparatus to make the ratio of the amount of air to the amount of liquid larger to a volume ratio of 1000:1, there is the problem of stable generation of mist becoming difficult.
When utilizing an atomization apparatus having this characteristic for an application such as cooling utilizing the latent heat of evaporation (heat of vaporization) without wetting the object for cutting or other processing, large particles of liquid deposited on the cooled surface, the cooling efficiency was inhibited, a large amount of ineffective liquid (chemical) was consumed, and environment problems were caused. To improve on this point, a system of dropping a liquid into a flow of air such as used for feeding fuel in a combustion engine etc. may be considered, but there would be the problems of the apparatus becoming large and a stable particle distribution and concentration not being able to be obtained. A satisfactory cooling effect could not be obtained.